US1683210A - Motor-control apparatus - Google Patents

Description

Sept. 4, 1928. 1,683,210

I c; c. RUNNER MOTOR con'moug. APiARATUs Filed Aug. 6, 1925 lZOm Invent or 1 Claude C. Qunhen' Hts Attorney.

Patented Sept. 4.192s.

IUNlTED' STATES CLAUDE O. RUNNER,

PATENT orrlca OF SOHENEG'IADY, NEW YORK, ASSIGNOB TO GENERAL ELEUI'RIG :11am, A. CORPORATION 01' NEW YORK.

' uoron-comndr. Arranurus.

Application filed Augult My invention relates to the control of electric motors and provides improved control apparatus for connecting the motors to a source ofcurrent and automatically limiting I the current of the motors during the starting period.

Although well adapted for controlling a single motor of a type that requires limitation of the motor starting current, the control apparatus embodying the present invention is particularly advantageous in .controlling a plurality of motors which it is desired to start successively with the starting current of each motorof limited value. By means of the present invention the starting current of each of a plurality of motors may be limited by a single current limiting resistor.

In carrying the invention into efiect in a control system for a plurality of motors, a separate line switch is provided for connecting each motor to a source of supply and in accordance with the preferred form of the invention, a current llmlting resistor is con-- 2 nected in the circuit through which all the -motors are supplied with current. The current limiting resistor is normally short circuited by a switch which is arranged to be operated so as to insert the resistance in the motor circuit prior to operation of each of the motor line switches thus insuring that the starting current oi each motor .is of limited value. A time element device automaticallycontrols the resistor short circuiting switch in such manner that the short circuit around the current limitin resistor is reestablished a predetermined time interval after each insertion of the resistor in the motor circuit. Y

Although not necessarily limited thereto, the present invention is well adapted for controlling a group of motorsdriving amachine such. for example, as a multi cutter head woodworking machine. Where-the control 5 apparatus, as well as the driving motors, is mounted upon the driven machine my-invem tion permits a considerable reducti'on in the space required for the controlling apparatus. Inthe accompanying drawing the single vfigure is a schematlc diagram of a control system'embodyingmy inventionv in a form suitable for controllinga plurality of electric motors... The control. system illustrated is designed for controlling the several driving s, 1925. Serial m. 48,638.

motors of a multi cutter head woodworking machine. Referring to'the drawing, the electric drivmg motors 10, 11 and 12, are shown as of the three phase alternating current induction type, although the present invention maybe applied with equal advantage to control other in detail in the drawing, it will be understood that each of the motors 10, 11 and 12 may be connected to drive one of the cutting heads of a multi head woodworking machine.

The group of electric motors comprising the.

motors 10, 11,12 is arranged to be supplied with power from either the low frequency supply lines L or the hi h frequency supply pes of motors. While not shown lines L through a suita 1e selective switch A 13. The electroresponsite line switches 14,

15 and 16 are provided for connecting the motors 10, 11 and 12 respectively to either supply lines L or L depending upon the previous operation of the selective switch 13.

In order to limit the current supplied to each of the motors 10, 11, 12, during the starting period, the current limiting resistors 47 are connected in the circuit through which the motors are supplied with power and the electroresponsive switch 18 is provided for short circuiting the resistors47 during normal operation of the motors.

In accordance with the present invention the electroresponsive switch 18 which controls the short circuit around the currentlimiting resistors 47 is normally closed so as to short circuit the resistors 47 before and during operation of an one of the group of motors 10, 11, 12. us when the switch 18 is of the type which is operated to the closed position upon en'er' 'zation of the operating winding thereo as shown in the drawing, the operating winding of the switch is connected so as to be energized before, as well as during, the operation of any of the grou of motors 10, 11, 12, as will be more mi} the operation of the control system illustrated. It will be understood, however, that if desired the resistance controlling switch 18 may be of the type which is normally biased to the closed position, and operated t5 the open position'upon the energization of the operating winding. In either case suitable time element means are provided for maintaining the short circuit around the described in connection with and assigned to the assi nee o resistors 47 open for a predetermined time interval.-

In the arrangement shown a time element relay 19 of the type fully described and broadly claimed in Patent No. 1,638,372, issued August 9, 1927 to George E. Stack, my present invention, is provided or controlling the switch 18. As will be more fully described hereinafter, the time element control arrangement is such that the current lim1t1ng resisters47 are maintained inserted in the circuit throu h which power is supplied to the group motors 10, 11 and 12 vfor a predetermined time interval during the startin of each motor in the group.

It Wlll be seen that the time element relay 19 is provided with a winding 20 for o crating the normally open contact 21 to t e closed positionland the winding 22 serves to retard the o eration of the contact 21 by periodically ho ding and releasing the movable magnetic member 23 when energized from an alternating current source. I would have it understoo however, that my present invention is not limited to any particular type of time delay means for controlling the operation of the resistance short circuitinglswitch 18.

otors 24 and .25 also are shown as of the three phase alternating current type and are mechanically shown in the drawing to individually drive a cutting head of the woodworking machine.

, The motors .24 and 25 are arranged to be supplied with ower only from the low frequency supply ines L, and these motors are of such a size that they may be connected directly to the su ply lines upon operation of the correspon ing electroresponsive line switches 26 and 27.

It will be observed that the electric motors 10,11, 12, 24, 25 are protected by means of the thermal responsive devices 28, 29, .30,

31,32, respectively, each of which is connected to be heated in accordance with-the.

switches 14, 15 and 16 respectively, and,

thereby control the starting of the corresponding motors 10, 11, 12. a The line switches 26 and 27 of the corresponding motors 24 and 25 are'controlled by the manu- -al1 operated push buttons or master swltches' 36 and 37 respectively. It will be seen that the motor starting push buttons 33, 34, and 36, are of the two-position type having both upper and lower contacts, and are normally biased into engagement ep'nnected by means not tacts are closed. The'stopping of all of 74 the motors 10, 11, 12, 24 and 25, is controlled by the normally closed push button 38, as well as by the undervoltage protective relay 39, which is energized responsively to the voltage impressed upon the group of 7:

motors 10, 11 and 12 as shown in the drawing. The motor 25 may be stopped separately by operation of the pormally closed push button 40.

The operation of the control system illus- 8 trated is as follows: With the supply line L energized from a suitable alternatm current source of suitable frequency, sue for example, as cycles, and the supply lines L energized from an alternating current 8 source of a relatively higher frequency such, for example, as cycles, the selective switch 13 may be operated to sup ly power to the oup of motors 10, 11- an 12, from either t e supply lines L or the su ply lines 9 L This permits the cutter hea s of the woodworking machine to be driven by the motors 10, 11, 12 at either low speed or high speed, I depending upon the nature of the icutting operation, as well as the nature of 9 the wood bein operated upon.

Assuming t at the selective switch 13is operated to its lower position to operate the group of motors 10, 11 and 12, from the igh frequency supply lines L,, the under- 1 voltage responsive relay 39 then is energized by the voltageacross one phase of the suply lines L and o crates to the circuit closmg position. T1115 at once establishes an energizing circuit for the operating winding 1 20 o the time element relay 19 which may be traced from the right hand supply line L through the conductor 41, the contacts of the several termal overload rotective devices 28, 29, 30, 32 and 31, and t ence through 1 the contact of the 'undervoltage relay 39, the normally closed push button 38, the upper contacts of the several motor starting push buttons 33, 34 and 35, the conductor 42, the operatin windin 20 and the conductor 1 43 to the mi dle supp y line L,. The resultmg energlzation' of the operating winding 20 starts operation of the contact 21 to the closed position. At the same time, the retardlng winding 22 of the time element re- I lay 19 and the operating winding of the res1stance controlling switch 18 are energized n parallel circuit with the operating windmg 20. v It will be observed that the retarding wlndmg 22 and the operating winding of switch 18 are energized in series circuit. In thls way the resistance of the retarding w1ndmg22 serves to limit the current passmg through the operating winding of switch 1 18 to a-value which is in'sufiicient to efiect operation ofthe switch 18 to the closed'position. However, the current passin through the retardi'n to peri'odica g 23 and there inding 22 is of suflicient value attract ,the magnetic member delay the operation of the contact 21 to t e'closed position for a prede-,

termined time interval. When the contact 21 is closed the retarding winding 22 is short operated tothe closed position to short cirthrough the conductor 41, contacts of the cuit the current limiting resistors 47.

With the .switch 18 thus operated to its initial osition in which the current limiting resistors 47 are short circuited any one of the motor starting push buttons 33, 34, 35, may be operated .to set the corresponding motors 10, 11, 12, into operation, although it will be observed that the push button starting switches are interlocked electrically so' that onlya single motor can be started at any one time.

If the motor 10 is to be started first, the starting push button 33 is depressed. As the push button 33 disengages its upper contacts the energizing circuit throu h the conductor 42 for the operating win ing of the resistor controlling switch 18 is interrupted and switch 18 immediately opens to insert the current limiting resistor 47 in the circuit prior to the connection of the motor 10 thereto. As the push button 33 engages with its lower contacts an energizing circuit for line switch 14 is established extending thermal devices 28 to 32, the undervolta e relay 39, the normally closed stop pus h button 38, the push button 33 in its lower position, the operating winding of line switch 14, and the conductor 43. The resultmg closure of line switch 14 simultaneously establishes a holding circuit through the auxiliary contact 44 with which the switch 13 provided and connects motor 10' to the supply lines L, with the current limiting resistors 47 in the motor circuit. The motor 10 at once starts and soon accelerates to normal running speed, the starting and the accelerating current of the motor being limited to a suitable value by the resistors 47.

When the uppercontacts of the-push button 33 were opened to deenergize the switch 18 and thereby inserting the resistors 47 in the motor circuit, the operating winding 20 of the time element relay 19 also was deenergized, thus permitting the contact 21 to immediately return to the open position in which it is shown. However, as soon as the resistance controlling switch 18 is opened, the winding 20 at once is reenergized through the auxiliary contact 45 with which the switch 18 is provided. Thus, upon the opening of'the switch 18 to insert the resistors in the motor circuit, the contact 21 of thetime element rela 19 immediately is set into operation to t e closed osition to reenergize the operating win ing of switch 18 after terval.

- In case the. motor-starting push button 33 a predetermined time inis not released so as to close its upper contacts before the contact 21 of the time element relay 19 is operated to the closed position, the switch 181 is energized only .18 at recurring interva s.

However, when the motor startingpush.

button 33 is released as soon as the motor 10 is started and before the time element relay 19 operates to close its contact 21, as/will be the case under all ordinary operating conditions, the switch 18 is maintained in the open position only for the time interval required for operation of the relay 19. This is dueto the fact that the push button 33 in its upperposition maintains the operating winding of switch 18 energized through a circuit which is in shunt circuit with the auxiliary contact 45 of the switch 18. Thus, under normal operating conditions the switch 18 and the time element relay 19 function to maintain the current limiting resistors- 47 effective to limit the current of the motor for only a predetermined time interval after the motor is connected to the source of supply.

After motor 10 is set into operation with the current limiting resistors 47 in circuit with the motor for a predetermined time interval during the'starting period, one of the motors 11, 12, may be set into operation by depressing the corresponding push buttons 34 or 35. When one of the push. buttons 34 or 35 is depressed the switch 18 again is operated just prior to the connec tion of the corresponding motor to the supply lines so as to insert the current limiting resistors 47 in the motor circuit for a predetermined time interval in exactly the same manner as previously described in connection with the starting of the motor 10. In each case the switch 18 responds when the push button disengages its upper ment relay 19 serves to delay reclosure of the switch 18 and thus maintains the short circuit around the current limiting resistors 47 en for a predetermined time interval.

, sired limits and the resistor controlling switch .18 is returned automatically to its initial position a time intervalafter each motor is started. 7

With the selective switch 13 operated so as to energize the group of motors 10, 11, 12 from the low frequency supply lines L the operation of the motor controlling switch mechanism illustrated is exactly the same as previously described exce t that the undervoltage protective relay 39 1s energized responsively to the voltage of the supply lines L and hence no further descrip: tion is necessary.'

' The motors 24, 25, may be set into operation at an time the undervoltage relay 39 is closed y depressing the COITQSPOILdHIg motor starting push button 36 or 37. In each case the motor is connected directly to the lowfrequency supply lines L since the motors are of such a size as to not require limitation of the starting current thereof As previously pointed out, any of the motors 10, 11, 12, 24, 25, which may be in operation are stopped upon operating the normally closed stop push button 38, while the motor 425 may be individually stopped by operating the normally closed stop push button 40 v v fWhile I have described and illustrated the preferred embodiment of vmy invention, it will be evident to those skilled in the art that various changes and modifications may be. made therein without departing from the spirit of the invention or from ,the scope of the ap ended claims.

What I claim as new and desire to secure by Letters Patent of the United States is 1. In amotor control system, the combination withv an electric motor, of means including a switch operable from one position to a second position 'for' connect ng the moto'rto a source of current upon operation of said switch to said second ition and return thereof to the first pos1tion,-means for limiting the current of the motor, said means normally being inefiective, and means I set into operation upon operationof said switch from said lone position for rendering. said current l1m1t1 means efiective prior to operation of sai switch to said second position and" for a predetermined time 1nterval after the return of said switch to said one 2. nationwith an electric motor, of electroosition. Y I I a-motor control system,-the COmbP responsive startin switch mechanism for f hemot ea l m the current of the motor during starting,'said means nor-,

mally being ineffective, a control switch current ofthe motor, an electro time element circuit controlling device for I trolling switch to.said one position in accordance with its bias. 1 4

- 3. In a motor control system, the combination with an electric motor, of electroresponsive starting switch mechanism for connecting ,the motor to a source of supply, a control switch therefor operable from'one nected to eflfect operation of the electroposition to a second position for cheating 7,

operation of said starting switch mechamsni, a normally short, circuited resistor in circuit with the motor, andiibrmally ener-' gized time elemen electrbresponsive switch mechanism'under t e control of said control ,switch and arranged -to-vbe de-energized to remove the short circuit from, said resistor prior to the operation ofsaid starting switch mechansim to start the motor and to maintain. the short circuit removed from said resistor for a predetermined time interval A 4. In a motor 0 ntrol system, the combination with an electric" motorf-qf electroresponsive line. switch, for connecting the mo'tor,to a source of cufnent, a normally energized electr'oresponsive switch operable upon deenergization'thereof from an initial position to another position to limit the current of the motor, a common control switch for successively-deenergizingsaid current limiting switch and energizin said line switch to start the motor wit limited current, and. time element circuit controlling meansset into operation under the control of said common control switch for automatically efiecting the return of the current controlling switch to-said position aftera timeinterval.

. 5. In a motor control system,--the combination with an electricmotorgof an electroresponsive line switch for connecting the motor to a source'of current a normally energized electroresponaive SWltCh operable upqn de-energization thereof from an-initial position to nsive all another position to-lir'nitj the u automatically controlling of said ,currentlimiting switch er oertain conditions, a masterf switch having two by said master switch and said time element device whereby the said line switch is energized to connect the motor to a source of current after de-energization of the said current limiting switch to effect operation thereof to said other osition and. the said current limiting switc gized to effect the return thereof to the said initial position after a predetermined time interval.

6. In a motor control system, the combination with a plurality of electric motors having a common supply circuit, of a common current limiting means connected in the common supply circuit for the motors, switch mechanism for successively connecting the motors to said common supply circult, and cooperating switch mechanlsm and connections whereby the said current limiting means is inserted in the supply circuit when each motor is connected thereto.

7. In a motor control system, the combination with a plurality of electric motors having a common supply circuit, of a separate switch for connecting each motor to said common supply circuit, a normally short circuited current limiting resistance connected in the common supply circuit for the motors, and electrore'sponsive circuit controlling means jointly controlled by said separate switches and arranged to open the short circuit around said resistance prior to the connection of each motor to the common upply circuit.

8. In a motor control system, the combination with a plurality of electric motors,

of separately operable line switch mechanism for each motor separate operating a means for each line switch, a common current limiting resistor connectedin the supply circuit for the motors, a normally closed electroresponsive switch for short circuitin said resistor before and during operation each motor, connections whereby the said electroresponsive switch is operated to the open position to insert said resistor in the supply circuit of the motors upon operation of the corresponding operating means of each of said line switches to start the corresponding motor, and time element means set into operation upon each opening of said is re-enerby upon operation of any master switch the I having a common supply line, of a .current limiting resistance connected in the supply line for the motors, a se arate electroresponsive line switch for eac motor, a separate master switch for controlling each lme switch, a normall closed electroresponsive switch for short circuiting the said resistor, a time element circuit controlling device associated with said normally closed electroresponsive switch and arranged to be set into operation upon the operation of said switch'to the open position, and connections jointly controlled by each master switch and said time element device whereby the said normall closed electroresponsive switch'is operate to the open position upon operation ofany master switch to effect operation of the corresponding motor line swltch and is reclosed after a predetermined time interval.

11. In combination in a system of motor control, a plurality of electric motor having a common supply circuit, selectively operable switch mec anism for connecting said motors to said common su ply circuit ina sequence as determined by t e operation of said switch mechanism, a common automatically operated acceleration controlling means connected in the common supply circuit for said motors, and, connections between said switch mechanism and said means necessitating that each of said motors be placed under the control of said means 'upon the connection of the motor to the common supply circuit.

12. In combination in a system of motor control, a plurality of electric motors having a "common supply circuit, selectively operable switch mechanism'efi'ective to connect said motors to said common supply circuit in an order determined by the order of operation thereof, a common automatically operated acceleration controlling means con- 'nected in the common supply circuit for said motors, and connections between said swltch mechamsm and said means requiring said means to be m operative cond1t1on pr1or to the connection of each motor to the common suppl circuit and necessitating that each of sai motors be placed under the control of said means upon the connection of the motor to the common supply circuit.

In witness whereof I have hereunto set my hand this 5th da of August, 1925.

, CLA E G. RUNNER.

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